In sheet metal stamping production lines a stack of sheet metal blanks is delivered to the front of the line in a stack. The blanks in the stack tend to adhere to each other as a result of a vacuum effect caused by the lack of air between adjacent blanks and a film of oil between the adjacent blanks. Individual steel sheet metal blanks may be separated by fanner magnets that fan apart the edges of several of the top blanks to eliminate the vacuum effect created by stacking the blanks because there is no air between adjacent blanks. Vacuum cups located above the top blank are utilized to pick up the top blank and transfer the top blank to downstream automation equipment to feed the blank to a press.
Aluminum sheet metal blanks, or non-magnetic sheet metal blanks, may be separated in the same way but the fanner magnets are relatively ineffective for separating aluminum blanks. Instead of fanner magnets, an air knife may be used that directs a stream of air at the top of the stack of blanks to inject air between the top blank and the stack. The air separates the top blank from the stack and eliminates the vacuum effect, but dirt dust particles, or slivers from the blanking operation at the edge of the stack of blanks may be blown onto the surface of the blanks. Even small dust particles or slivers on the surface of the blanks create visible surface imperfections when the blank is drawn in a draw press or formed in another forming operation.
This disclosure is directed to solving the above problems and other problems as summarized below.